MadeEasy Subject Test: Databases - Er Diagram

Question

what will be the key for total participation 1:1 combining tables??? plz give the Candidate keys and foreign keys seperately??

Also what if in 1:1 relation total participation is on both side than what will be key?? Composite key to both tables or key of anyone table will be selected???

Comments

3 relation?

---

Only 2 table are required. total participation in 1:1 so those relations along with relation merged n single table. And one for another entity E3 with relation.

Answer 1

There will be two tables at the end.

E1RE2 will be combined into one table and E3R2 will be combined into one table.

For the E1RE2 table,primary key will be the primary key of E2 i.e D and there will be no foreign key.

For the table E3R2 there will be two primary keys D and G and D will be the foreign key to the table E1RE2.

For the total participation on both sides, everything will be same except the primary keys.Now table E1RE2 can have two keys D and A.